Method for adjusting the rotational speed of an internal combustion engine of a road-building machine, and road-building machine for said method

ABSTRACT

A method for adjusting the rotational speed of an internal combustion engine of a road-building machine which, in addition to a traction drive, has hydraulic motors which are connected to the internal combustion engine and which serve for driving working assemblies, in which method the rotational speed is adjusted as a function of the present power demand of the working assemblies, characterized in that the hydraulic motors are operated using fixed-displacement pumps, and residual volume flows presently to be discharged are reduced by flow valves for hydraulic motors of active working assemblies, for which purpose the rotational speed of the internal combustion engine is automatically adapted during working operation.

The invention relates to a method for adjusting the rotational speed ofan internal combustion engine of a road-building machine, according tothe preamble of claim 1, and a road-building machine having an internalcombustion engine, according to the preamble of claim 7.

From DE 39 11 401 C1 it is known that, in a road finisher, therotational speed is in practice regulated manually by the driver. Intransport journeys and transfer journeys, the power of the diesel engineis needed mainly for the traction drive. Different driving situationsare taken into account by the driver by continuous regulation of therotational speed of the diesel engine. For paving-working operation, thediesel engine runs, however, at the nominal rotational speed. The drivergenerally makes no adjustments, since he is unaware of the actual powerrequirement and must avoid a situation in which working assemblies whichare required during interruptions have not been supplied with thenecessary power. The environment is unnecessarily polluted by noise andexhaust gases. Fuel is also wasted unnecessarily.

In order that, during operation of the road finisher, the environmentalpollution and fuel consumption are reduced without demanding theattention of the driver, it is known from DE 39 11 401 C1 toautomatically adapt the rotational speed of the diesel engine, duringinterruption of the paving-driving operation, to the power requirementof the working assemblies. The adaptation can here be conducted suchthat, dependent on the current power requirement, intermediaterotational speed values between the two limit values of the nominalrotational speed and the idle speed can be set. The rotational speed isadapted to the current power requirement by means of an adjustingdevice. Upon interruption or after interruption of the paving-drivingoperation, the rotational speed is immediately adapted by means of theadjusting device without influence of the driver being necessary in thisprocess. During paving-driving operation, the rotational speed of thediesel engine is accelerated to the nominal rotational speed and ismaintained without change. The environmental pollution by noise orexhaust gases is perceptibly reduced.

From WO 2010/006759 A1 it is known that, for laying the road surface,above all the traction drive of the road finisher, the drive for thetamper bar and/or the vibrators are operated at constant rotationalspeed or frequency in order that the road surface produced by the roadfinisher does not change. If, for this purpose, the internal combustionengine is operated at constant rotational speed, the internal combustionengine frequently, however, generates too much energy. In order tooperate the road finisher economically, the rotational speed of theinternal combustion engine is raised or lowered in such a way that theenergy which is required for a paving condition in order to keep therotational speed or frequency constant is supplied these drives whichare to be kept constant. Other drives, for instance for the conveyor fortransporting the material of the road surface and for the spreadingaugers, can change with the alteration of the rotational speed of theinternal combustion engine, since these have no influence on the laidroad surface. The power requirement of the drives which are to be keptconstant is measured and, with that, the rotational speed of theinternal combustion engine is altered by means of a control system, sothat said internal combustion engine generates as much more or lessenergy as to compensate the changed energy requirement of the driveswhich are to be kept constant. In this context, it is disadvantageousthat the load-dependent change in the rotational speed of the internalcombustion engine is determined by keeping at least one driveapproximately constant. The increase or reduction in the rotationalspeed of the internal combustion engine is governed by how much energyis required in order that with changing loads, for example rising orfalling slopes, the drives which are to be kept constant are kept atleast approximately constant. Here too, the internal combustion engineof the road finisher frequently generates too much energy, since thepreset of the at least one drive which is to be kept approximatelyconstant adversely restricts the load-dependent adjustment of therotational speed of the internal combustion engine.

The object of the invention is therefore to provide a method foradjusting the rotational speed of an internal combustion engine of aroad-building machine, and a road-building machine for said method,which allow an economical operation of the road-building machine.

This object is achieved by the features of claims 1 and 7.

A method and a road-building machine is hereby provided, in which therotational speed of the internal combustion engine is automaticallyadapted to the respective current power requirement of the activeworking assemblies in the paving-working operation. The rotational speedof the internal combustion engine is adjusted to such a rotational speedat which the residual volume flows of fixed displacement pumps fordriving hydraulic motors are reduced. The reduction is preferably aminimization in such a way that the residual volume flow of the at anyone time highest loaded working assembly, i.e. where the largest volumeflow is present, is approximately zero.

The currently highest necessary volume flow at any one time can be usedas a measure of the possible reduction in rotational speed relative tothe nominal rotational speed of the internal combustion engine. Theinternal combustion engine thus forms a real flow regulator, which iscontrollable by means of the adjustment of its rotational speed. Theengine power is usually constant within a large range of rotationalspeed, so that the rotational speeds can be varied.

The traction drive is fed by means of an independently adjustablehydraulic pump. The paving speed is adaptable to whether the degree ofload-dependent energy saving is fully or only partially utilized.

The use of flow control valves in conjunction with fixed displacementpumps is a cheaper solution than the use of variable displacement pumps.The fixed displacement pumps ideed always generate the full volume flow,so that the residual volume flow which is not required has to bedischarged via a valve. However, according to the invention the losseswhich are herein incurred are reduced, so that this drawback is remediedby the inventive energy optimization measure.

Preferably, the flow control valves of the active working assemblies areconnected to a controller, which varies the residual volume flows in aload-dependent manner, wherein the highest volume flow can be made to aresidual volume flow of approximately zero via the adjustment of therotational speed of the internal combustion engine. The associated flowcontrol valve is then, for instance, fully open.

Further embodiments of the invention can be derived from the followingdescription and the subclaims.

The invention is explained in greater detail below with reference to theillustrative embodiment represented in the appended drawing.

FIG. 1 shows a block diagram for the adjustment of the rotational speedof an internal combustion engine of a road-building machine.

As shown in FIG. 1, the invention relates to a method for adjusting therotational speed of an internal combustion engine 1 of a road-buildingmachine, in particular of a road finisher, a road milling machine or thelike, which, in addition to a traction drive 2, has hydraulic motors 3,connected to the internal combustion engine 1, for the driving ofworking assemblies. In a road finisher, the working assemblies include,for instance, a tamper bar, a vibration device for a screed, a conveyorbelt for material to be laid, and a spreading auger, which, moreover,are able to be provided in multipart or multiple arrangement.

The rotational speed of the internal combustion engine 1 can be adjusteddependent on the current power requirement of the working assemblies,for which purpose the internal combustion engine 1 has a rotationalspeed adjusting device 4.

The hydraulic motors 3 are operated using fixed displacement pumps 5.The fixed displacement pumps 5 always generate the full volume flow fora specific rotational speed of the internal combustion engine. Theamount of the constant volume flow is set by the rotational speed of theinternal combustion engine 1.

Since the fixed displacement pumps 5 always generate the full volumeflow, a residual volume flow which is not required for the respectivehydraulic motor 3 that is to be fed is discharged via a flow controlvalve 6. The residual volume flows of the flow control valves 6 forhydraulic motors 3 of active working assemblies, which residual volumeflows are currently to be discharged dependent on a paving-workingoperation of the road-building machine, are now reduced according to theinvention, for which purpose the rotational speed of the internalcombustion engine is automatically adapted during paving-workingoperation. An increase or reduction of the rotational speed of theinternal combustion engine 1 increases or reduces the volume flow of thefixed displacement pumps 5. By means of the adjustment of the rotationalspeed of the internal combustion engine 1, the volume flow of the fixeddisplacement pumps 5 is consequently altered such that the residualvolume flows of the fixed displacement pumps 5 are influenced in anenergy-optimized manner. In paving-working operation, the internalcombustion engine 1 is consequently no longer operated at the nominalrotational speed, but at a rotational speed which is set on aload-dependent basis and is dependent on the power requirement of theactive working assemblies. The power requirement or energy requirementis here, in particular, a volume or rotational speed requirement.

To this end, a controller 7, which conducts an adaptation of therotational speed of the internal combustion engine 1 via a rotationalspeed signal line 8, is provided.

The adaptation is preferably realized such that the flow control valve 6of the hydraulic motor 3 of the currently highest loaded workingassembly, having then the smallest residual volume flow, gives thesetting of the rotational speed signal for the adjustment of therotational speed of the internal combustion engine 1. The optimizationof energy usage by adjustment of the rotational speed of the internalcombustion engine 1 can be done to the point where at least one,preferably the smallest of the residual volume flows, is brought toapproximately zero. The remaining residual volume flows inevitablyfollow this degree of adjustment and are likewise reduced. Since theenergy requirement of the hydraulic motors 3 for the various workingassemblies in paving-working operation is different, the degree of thereduction of the residual flows is likewise different. The controller 7adjusts the flow control valves 6 via a control line 9.

The reduction of the residual volume flows of the flow control valves 6of a plurality of hydraulic motors 3 can be linked in the manner of amaster-slave architecture, according to which the residual volume flowof the flow control valve 6 of the hydraulic motor 3 of the currentlyhighest loaded working assembly determines the setting of the rotationalspeed signal as the master, which the flow control valves 6 of thehydraulic motors 3 of the other active working assemblies follow asslaves.

Preferably, at least the residual volume flow of the at any one timehighest loaded working assembly is minimized or adjusted approximatelyto zero. The highest consumer then receives the full volume flow of theassociated fixed displacement pump 5 as a result of the appropriatelyadjusted rotational speed of the internal combustion engine 1, while theflow control valves 6 can still discharge residual volume flows, whichthen, however, are at least reduced. The road-building machine isthereby operated more economically.

The current power requirement of individual working assemblies isdetected and notified to the control device 7. By means of sensors 10,which are connected via data lines 11 to the controller 7, the energyrequirement of the individual active working assemblies duringpaving-working operation can be continuously determined and delivered asinput data to the controller 7 for an automatic load-dependentadaptation of the rotational speed of the internal combustion engine 1.

For the traction drive 2, an additional hydraulic pump 12 is provided inorder to be able to adjust the traction drive independently from therotational speed of the internal combustion engine 1. Via control lines13, 14, the controller 7 can adjust the traction drive independentlyfrom the energy-optimized adjustment of the rotational speed of theinternal combustion engine 1, since also an energy-optimized reductionof the rotational speed of the internal combustion engine 1 relative toits nominal rotational speed in a paving-working operation providessufficient power for the traction drive 2 to enable adjustment to aselectable running speed.

For the implementation of the above-described method, a road-buildingmachine, in particular a road finisher, having an internal combustionengine 1 for driving a traction drive 2 as well as a plurality ofhydraulic motors 3 for working assemblies (not shown), is provided. Inaddition, a control apparatus for a controller 7 for adjusting therotational speed of the internal combustion engine 1 dependent on thecurrent power requirement of the working assemblies is provided.

Each of the plurality of hydraulic motors 3 can be operated by means ofa fixed displacement pump 5, which is drivable by the internalcombustion engine 1 and the full volume flow of each of which can beinfluenced by means of a respective flow control valve 6, and thecontroller 7 of the control device is connected as a connecting linkbetween the flow control valves 6 of the hydraulic motors 3 and arotational speed sensor of the internal combustion engine 1 and has anadaptation control circuit, which provides a rotational speed signal setto a reduction of the residual volume flows of the flow control valves 6for hydraulic motors 3 of active working assemblies, which residualvolume flows are currently to be discharged.

The adaptation control circuit for making a selection can be designedsuch that the flow control valve 6 of the hydraulic motor 3 of thecurrently highest loaded working assembly, having then the smallestresidual volume flow, gives the setting of the rotational speed signalfor the adjustment of the rotational speed of the internal combustionengine 1.

The adaptation control circuit can be designed for linking the reductionof the residual volume flows of the flow control valves 6 of a pluralityof hydraulic motors 3 in the manner of a master-slave architecture.

1. A method for adjusting the rotational speed of an internal combustionengine of a road-building machine, which, in addition to a tractiondrive, has hydraulic motors, connected to the internal combustionengine, for the driving of working assemblies, and in which method therotational speed is adjusted dependent on the current power requirementof the working assemblies, wherein the hydraulic motors are operatedusing fixed displacement pumps and residual volume flows of flow controlvalves for hydraulic motors of active working assemblies, which residualvolume flows are currently to be discharged, are reduced, for whichpurpose the rotational speed of the internal combustion engine isautomatically adapted during working operation.
 2. The method accordingto claim 1, wherein the adaptation is done such that the flow controlvalve of the hydraulic motor of the currently highest loaded workingassembly, having then the smallest residual volume flow, gives thesetting of the rotational speed signal for the adjustment of therotational speed of the internal combustion engine.
 3. The methodaccording to claim 2, wherein the reduction of the residual volume flowsof the flow control valves of a plurality of hydraulic motors is linkedin the manner of a master-slave architecture, according to which theresidual volume flow of the flow control valve of the hydraulic motor ofthe currently highest loaded working assembly determines the setting ofthe rotational speed signal as the master, which the flow control valvesof the hydraulic motors of the other active working assemblies follow asslaves.
 4. The method according to claim 1, wherein at least theresidual volume flow of the at any one time highest loaded workingassembly is minimized.
 5. The method according to claim 1, wherein thecurrent power requirement of individual working assemblies is detectedand notified to the control apparatus.
 6. The method according to claim1, wherein the traction drive is operated independently from therotational speed of the internal combustion engine.
 7. A road-buildingmachine having an internal combustion engine for driving a tractiondrive as well as a plurality of hydraulic motors for working assemblies,and having a controller for adjusting the rotational speed of theinternal combustion engine dependent on the current power requirement ofthe working assemblies, wherein each of the plurality of hydraulicmotors can be operated by means of a fixed displacement pump, which isdrivable by the internal combustion engine and the full volume flow ofeach of which can be influenced by means of a respective flow controlvalve, and the controller is connected as a connecting link between theflow control valves of the hydraulic motors and a rotational speedsensor of the internal combustion engine and has an adaptation controlcircuit, which provides a rotational speed signal set to a reduction ofthe residual volume flows of the flow control valves for hydraulicmotors of active working assemblies, which residual volume flows arecurrently to be discharged.
 8. The road-building machine according toclaim 7, wherein the adaptation control circuit is designed for making aselection according to which the flow control valve of the hydraulicmotor of the currently highest loaded working assembly, having then thesmallest residual volume flow, gives the setting of the rotational speedsignal for the adjustment of the rotational speed of the internalcombustion engine.
 9. The road-building machine according to claim 8,wherein the adaptation control circuit is designed for linking thereduction of the residual volume flows of the flow control valves of aplurality of hydraulic motors in the manner of a master-slavearchitecture, according to which the residual volume flow of the flowcontrol valve of the hydraulic motor of the currently highest loadedworking assembly determines the setting of the rotational speed signalas the master, which the flow control valves of the hydraulic motors ofthe other active working assemblies follow as slaves.
 10. Theroad-building machine according to claim 7, wherein sensors, whichindicate the current power requirement of individual working assemblies,are connected to the controller.
 11. The road-building machine accordingto claim 7, wherein the controller is connected to a traction drivepump, which is driven by the internal combustion engine, in order toregulate a traction drive motor, which is fed by the traction drivepump, to a selectable running speed independently from the rotationalspeed of the internal combustion engine.
 12. A road finisher configuredaccording to claim 7, wherein the working assemblies are a tamper andvibrators of a paving screed, a spreading auger, and a conveyor of aroad finisher.